All of the different single sutural synostoses share in common the premature closure of one of the skull's sutures. In order to understand these conditions it is helpful to know a little bit about the normal growth of the skull. The skull is not a single bowl of bone; instead it is formed from a number of different bones. The junction where these bones meet, or come together, is called a suture. We know that sutures are very important in growing children. The skull probably does not grow on it's own; instead, it only gets larger in response to brain growth. Therefore, if the brain does not grow, the skull doesn't get larger. In the first few years of life, the brain grows very quickly. As the brain grows, it stretches the skull bones apart with the sutures acting like expansion joints. It is believed that this stretching of the sutures sends a signal to the skull bones telling them to grow bigger so that the skull can accommodate the enlarging brain (actually, the growth of the skull is slightly more complicated that this, and a simplified version is being presented). If one of these sutures has fused shut, the skull can not expand to accommodate the growing brain in the region of this fused suture so the brain must push the other sutures further apart so there is enough room to accommodate it's growth. This sequence of events leads to an abnormal skull shape. It is usually the identification of an abnormal skull shape that first tips off families, or their pediatricians, that something is going on with the skull.